Heat exchanger assembly and method for transporting thermal energy

ABSTRACT

A heat exchanger assembly to be introduced into a sewage pipeline includes: at least one first heat exchanger adapted to thermally contact a heat source with sewage and at least one second heat exchanger adapted to thermally contact the sewage with a heat sink. The at least one second heat exchanger is arranged along the sewage flowing direction in the sewage pipeline and spaced from the at least one first heat exchanger, as well as to a method for transporting thermal energy.

The invention relates to a heat exchanger assembly and a method for transporting thermal energy.

Energy recovery from sewage by heat exchanger devices subsequently installed in a sewage pipeline has been known from the prior art, the amount of thermal energy that can be recovered being dependent on the sewage temperature though, which deviates in addition. For example household sewage is warmer than rainwater, whereby the sewage temperature in a sewage pipeline decreases when it is raining, since small amounts of household sewage usually mix with larger amounts of rainwater. Due to the lower sewage temperature, the efficiency of energy recovery from sewage decreases at a thermal energy extraction point.

An object of the present invention is to provide a heat exchanger assembly, which is easy to produce and has an improved efficiency at the thermal energy extraction point, as well as a method for transporting thermal energy, which is easy to perform and increases the amount of thermal energy that can be recovered from sewage at the thermal energy extraction point. This object is achieved by the subject matters of the independent claims. Preferred embodiments are subject of the dependent claims.

Heat Exchanger Assembly

An aspect of the present invention relates to a heat exchanger assembly to be introduced into a sewage pipeline, comprising:

-   -   at least one first heat exchanger adapted to thermally contact a         heat source with sewage,     -   at least one second heat exchanger adapted to thermally contact         the sewage with a heat sink,         wherein the at least one second heat exchanger is arranged along         the sewage flowing direction F—i.e. downstream—in the sewage         pipeline and spaced from the at least one first heat exchanger.

Advantageously, the heat source is thermally connected to the heat sink. That is, thermal energy from the heat source is transferred toward the heat sink by means of the sewage flowing in the sewage pipeline. The term sewage particularly comprises rainwater, dirty water, and mixed water. The sewage pipeline is understood to be all volumina that contain the sewage, which particularly includes the sewage pipe itself, but also the sewage-technical constructions hydraulically connected thereto, such as weirs, throttles, collecting tanks, strainer devices, lifting systems, auxiliary pipelines, etc.

Starting from the heat source, thermal energy is transferred into the sewage present in the sewage pipeline by means of the at least one first heat exchanger. In other words, during proper use, the at least one first heat exchanger located in the sewage pipeline is thermally contacted in order to heat the sewage in the sewage pipeline. By means of at least one second heat exchanger, which during proper use is located in the sewage pipeline, the thermal energy is at least partially extracted from the sewage in order to transfer it to the heat sink. Advantageously, the heat source and the heat sink are located outside the sewage pipeline. The at least one first heat exchanger is arranged in a manner spaced from the at least one second heat exchanger in the sewage pipeline. The sewage flows along the sewage flowing direction F from the at least one first heat exchanger to the at least one second heat exchanger, wherein the sewage flowing direction F usually follows the slope of the sewage pipeline. In other words, the at least one second heat exchanger, with respect to sea level, is arranged deeper than the at least one first heat exchanger, or the second heat exchanger is located downstream of the first heat exchanger. In exceptional cases, the sewage is conveyed by means of a pumping system or at least one weir against the force of gravity and counter to the slope of the sewage pipeline, so that the sewage flowing direction F and thus the direction “downstream” is determined by the conveying direction of the pumping system.

Advantageously, by means of the heat exchanger device according to the invention, thermal energy can be transported from the heat source to the heat sink in a simple and cost-effective manner. Further advantageously, the heat exchanger assembly according to the invention is easy to produce, even if the distance between the heat source and the heat sink, or the first heat exchanger and the second heat exchanger, is relatively large, since the removal is performed between the first heat exchanger and the second heat exchanger through the already existing sewage pipeline. Thus, advantageously, assembly works are only necessary in the area of the heat source to install the at least one first heat exchanger, as well as in the area of the heat sink to install the at least one second heat exchanger, while the sewage pipeline between the first heat exchanger and the second heat exchanger remains unaffected. Due to the sewage pipeline being used, laying of separate supply lines, or transport lines, for transporting a heat exchanger medium between the heat source and the heat sink can be dispensed with. At the same time, the maximum distance between the heat source and the heat sink merely depends on the length of the already existing sewage pipeline and the heat losses occurring within the sewage pipeline. Thus, the transport of thermal energy by means of the heat exchanger assemblies according to the invention can be performed over distances of a few meters, or approximately 100 m, to several kilometers.

The at least one first heat exchanger and/or the at least one second heat exchanger is adapted to be in contact, i.e. at least in thermal contact, with the sewage in the sewage pipeline. The thermal contact designates the transition of thermal energy from the first or second heat exchanger into the sewage and vice versa. In addition to the thermal contact, the contact can in particular comprise direct wetting of the first and/or second heat exchanger by the sewage. Preferably, the area or part of the first heat exchanger and/or second heat exchanger in contact with the sewage is formed of a heat-conducting, rigid material, in particular of corrosion-resistant stainless steel.

It is appreciated that the outer shape or the form of the first heat exchanger and/or the second heat exchanger is designed such that it is adapted to the respective cross-section of the sewage pipeline concerned. Preferably, the first heat exchanger and/or the second heat exchanger are formed such that the heat exchangers can be introduced into the sewage pipeline through a conduit manhole and be displaced to the corner position. In other words, the first heat exchanger and/or the second heat exchanger comprise heat exchanger elements, which have little longitudinal extension, in particular of less than approximately 100 cm or approximately 65 cm, and of which the first heat exchanger and/or the second heat exchanger is assembled. Advantageously, it is not necessary in this case to expose the sewage pipeline via foundation ditches to mount the first heat exchanger and/or the second heat exchanger in the sewage pipeline.

Alternatively, the first heat exchanger and/or the second heat exchanger can be formed in the wall of a sewage pipeline segment. For example, the first heat exchanger and/or the second heat exchanger can be embedded in the wall of the sewage pipeline such that the contact surface of the first heat exchanger and/or of the second heat exchanger with the sewage in the sewage pipeline is formed as part of the sewage pipeline inner wall. Moreover, for example, the first heat exchanger and/or the second heat exchanger can be embedded in the wall of the sewage pipeline such that the heat exchange between the sewage and the first heat exchanger and/or the second heat exchanger is performed indirectly via the material of the sewage pipeline. Such segments of the sewage pipeline that are provided with a heat exchanger embedded therein can preferably be manufactured industrially, wherein these segments are used in the construction of the sewage pipeline, or wherein segments of an existing sewage pipeline are replaced by such segments provided with a heat exchanger.

Preferably, the heat exchanger assembly comprises a hot water forward-run line, or hot water advance piping, and a cold water return-run line, or cold water return piping, wherein a first heat exchange medium heated by the heat source can be supplied to the at least one first heat exchanger by means of the hot water forward-run line, and wherein the first heat exchange medium cooled by the at least one first heat exchanger can be supplied to the heat source by means of the cold water return-run line.

The transfer of thermal energy from the heat source into the sewage is preferably performed by means of a first heat exchange medium, which in a heated state is transported from the heat source via a hot water forward-run line, or hot water advance piping, to the heat exchanger. In order to transfer the thermal energy of the first heat exchange medium into the sewage, which thermally contacts the first heat exchanger, by means of the first heat exchanger, there has to be a thermal gradient between the first heat exchange medium and the sewage. In other words, there must not be a thermal balance between those two, but the sewage has to exhibit a lower temperature than the heat exchange medium. During proper operation of the heat exchanger assembly, the first heat exchange medium, which is heated by the heat source, is supplied continuously to the first heat exchanger by means of the hot water forward-run line. In the first heat exchanger, the first heat exchange medium cools down depending on the temperature of the sewage contacting the first heat exchanger in order to be fed back to the heat source via the cold water return-run line in the cooled state. Thus, the thermal energy from the heat source is transferred to the sewage. Preferably, circulation of the first heat exchange medium from the heat source to the first heat exchanger and back is achieved by means of a pump. Further preferably, the heat exchange medium substantially consists of water. Alternatively, oil or a different fluid with a sufficiently large thermal capacity can be used as the first heat exchange medium.

Preferably, the heat exchanger assembly comprises a cold water forward-run line, or cold water advance piping, and a hot water return-run line, or hot water return piping, wherein a second heat exchange medium cooled by the heat sink can be supplied to the at least one second heat exchanger by means of the cold water forward-run line, and wherein the second heat exchange medium heated by the at least one second heat exchanger can be supplied to the heat sink by means of the hot water return-run line.

To transfer thermal energy from the at least one second heat exchanger to the heat sink, a second heat exchange medium is heated in the second heat exchanger and supplied to the heat sink by means of a hot water return-run line, or hot water return piping. In order to utilize the thermal energy contained in the sewage, there has to be a thermal gradient between the sewage and the second heat exchange medium. That is, the sewage has to exhibit a higher temperature than the second heat exchange medium. For this reason, during proper operation of the heat exchanger assembly, the second heat exchange medium is cooled by the heat sink to a temperature lower than the temperature of the sewage. This cooled second heat exchange medium is fed continuously to the second heat exchanger by means of the cold water forward-run line, wherein the second heat exchange medium heats up in the second heat exchanger and is fed back to the heat sink via the hot water return-run line. Preferably, continuous circulation of the second heat exchange medium from the heat sink to the second heat exchanger and back is achieved by means of a pump. The second heat exchange medium substantially consists of water or an aqueous solution. Alternatively, oil or a fluid with a sufficiently large thermal capacity can be used.

Preferably, the heat exchanger assembly comprises a control unit, wherein the control unit is connected to a first temperature sensor, which is arranged downstream of the first heat exchanger and upstream of the second heat exchanger, and/or to a second temperature sensor, which is arranged downstream of the second heat exchanger.

Advantageously, the sewage temperature of the sewage in the sewage pipeline can be kept within a predetermined range by means of the control unit. Thus, it is advantageously prevented that too cold or too hot a sewage, starting from the second heat exchanger downstream, is transported within the sewage pipeline. Further advantageously, by means of the control unit, in connection with the first temperature sensor, it can be prevented that the sewage exceeds a predetermined sewage temperature by means of the first heat exchanger.

Preferably, the heat exchanger assembly comprises a second sewage pipeline, which is hydraulically connectable to the sewage pipeline, and at least one third heat exchanger adapted to thermally contact the sewage with a second heat sink, the respective sewage flow amount through the sewage pipeline and the second sewage pipeline being controllable.

It is appreciated that the heat exchanger assembly may also comprise a third sewage pipeline with a fourth heat exchanger, a fourth sewage pipeline with a fifth heat exchanger, etc., wherein the third and fourth sewage pipelines are each connectable to the sewage pipeline. Thus, advantageously a plurality of heat exchangers adapted to thermally contact at least one associated heat sink can be loaded with sewage, which can be heated by means of the heat source via the at least one first heat exchanger and be supplied via the sewage pipeline.

The second sewage pipeline being hydraulically connectable to the sewage pipeline means that the hydraulic connection can be interrupted at least from time to time, but be established if necessary. In particular, the hydraulic connection between the sewage pipeline and the second sewage pipeline can depend on the respective amount of sewage in the sewage pipelines.

Preferably, the heat exchanger assembly comprises at least one blocking device, which can make sewage coming from the first heat exchanger flow to the second heat exchanger and to the third heat exchanger in predetermined proportions. In other words, the at least one blocking device can control the hydraulic connection between the sewage pipeline and the second sewage pipeline. Here, the at least one blocking device can be formed in or on the sewage pipeline or be formed in or on the second sewage pipeline. In particular, the at least one blocking device can comprise a weir or a slider, or slidegate or gate valve, adapted to control the amount of sewage flowing through the sewage pipeline toward the second heat exchanger. The hydraulic connection between the sewage pipeline and the second sewage pipeline can be arranged upstream of the at least one blocking device, so that sewage from the sewage pipeline flows into the second sewage pipeline when the at least one blocking device in the sewage pipeline is closed. In particular, closing of the at least one blocking device in the sewage pipeline can cause the sewage from the sewage pipeline to rise counter to the slope in the second sewage pipeline therein toward the third heat exchanger. Preferably, the first heat exchanger is arranged at a higher level than the third heat exchanger in the second sewage pipeline, so that the sewage from the first heat exchanger flows along the sewage flowing direction F through the sewage pipeline up to the at least one blocking device, and then flows counter to the slope in the second sewage pipeline to the third heat exchanger, so that a transport of thermal energy from the first heat exchanger to the second heat exchanger can take place.

Further preferably, the at least one blocking device can be arranged in the second sewage pipeline, so that the entire amount of sewage coming from direction of the first heat exchanger remains in the sewage pipeline when the at least one blocking device is closed or partially closed.

Preferably, the heat exchanger assembly comprises a first flow control device, wherein the first flow control device is arranged downstream of the first heat exchanger. Preferably, the first flow control device can be a weir, a scouring valve, or a throttle. The first flow control device is adapted to control the amount of sewage that flows downstream. In particular, the first flow control device is adapted to dam accumulating sewage in the sewage pipeline being upstream with respect to the first flow control device. To this end, the first flow control device can vary the relative flow cross-section in relation to the flow cross-section of the sewage pipeline, preferably in a range from approximately 0% to approximately 100%. In particular, the relative flow cross-section of the first flow control device is infinitely adjustable at least in some part(s).

The first flow control device is preferably arranged directly downstream of the first heat exchanger in the sewage pipeline. Preferably, the first flow control device is arranged in a manner spaced from the first heat exchanger by less than 100 m, further preferably less than 50 m, and in particular less than 10 m.

Advantageously, the accumulating sewage can be dammed in the sewage pipeline in the area of the first heat exchanger by means of the first flow control device. Since the amount of thermal energy transferable from the heat source to the sewage by means of the first heat exchanger depends on the time of contact of the sewage with the first heat exchanger and substantially on the amount of sewage, the thermal energy transferable to the sewage can advantageously be increased by damming the sewage in the sewage pipeline in the area of the first heat exchanger. In particular, a sufficient amount of sewage can be stored in the area of the first heat exchanger by means of the first flow control device, so that a predetermined heat storage capacity in the sewage is provided in order to dissipate thermal energy accumulating at the heat source to the sewage via the first heat exchanger. In particular, it can be prevented that at times when the heat source is out of operation cool sewage flows past the first heat exchanger without being heated. By damming the sewage by means of the first flow control device, the cool sewage can be stored in order to be heated by means of the heat source via the first heat exchanger at a later time. Preferably, the first flow control device opens up the flow cross-section of the sewage pipeline at least partially when the dammed sewage has reached a predetermined amount or when the accumulated sewage has been heated to a predetermined temperature by means of the first heat exchanger. Thus, it can advantageously be guaranteed that draining by means of the sewage pipeline is ensured and that the highest possible amount of thermal energy can be transported by means of the sewage.

Further preferably, the heat exchanger assembly comprises a second flow control device, wherein the second flow control device is arranged downstream of the second heat exchanger. The operating principle of the second flow control device is analogous to the operating principle of the first flow control device. However, the second flow control device enables an improved utilization of the thermal energy contained in the sewage by means of the second heat exchanger. By damming the sewage in the sewage pipeline downstream of the second heat exchanger by means of the second flow control device, a larger amount of sewage can be provided to the second heat exchanger for a prolonged contact time. In this way, the thermal energy contained in the sewage can be extracted from the sewage particularly until a predetermined sewage temperature has been reached or is fallen below. Preferably, the second flow control device opens up the flow cross-section of the sewage pipeline at least partially when the sewage dammed upstream has reached a predetermined amount or a predetermined temperature. Further preferably, the second flow control device is arranged directly downstream of the second heat exchanger in the sewage pipeline. Further preferably, the second flow control device can be arranged in a manner spaced from the second heat exchanger in the sewage pipeline by less than 100 m, further preferably less than 50 m, and in particular less than 10 m.

Preferably, the heat exchanger assembly comprises a third flow control device, wherein the third flow control device is arranged downstream of the third heat exchanger. The effects, the preferred embodiments, and the preferred arrangement of the third flow control device correspond to those of the second flow control device.

Preferably, the heat exchanger assembly comprises a first measuring device, which detects the level H₁ above the first heat exchanger and/or the sewage temperature T_(W1) in the area of the first heat exchanger. Here, detecting the level H₁ can in particular comprise measuring the water level or sewage level in the sewage pipeline by means of ultrasound or by means of water pressure measurements. Detecting the sewage temperature T_(W1) particularly comprises measuring the sewage temperature by means of a temperature sensor.

Further preferably, the first measuring device is connected to the first flow control device, so that the first flow control device can be controlled on the basis of the data obtained by the first measuring device.

Preferably, the heat exchanger assembly comprises a second measuring device, which detects the level H₂ above the second heat exchanger and/or the sewage temperature T_(W2) in the area of the second heat exchanger. Further preferably, the heat exchanger assembly comprises a third measuring device, which detects the level H₃ above the third heat exchanger and/or the sewage temperature T_(W3) in the area of the third heat exchanger.

Detecting the levels H₂ and H₃ can in particular comprise measuring the respective water level or sewage level in the sewage pipeline by means of ultrasound or by means of water pressure measurements. Detecting the respective sewage temperatures T_(W2) and T_(W3) can particularly comprise measuring the sewage temperature by means of temperature sensors. The second and third measuring devices can be connected to the associated second and third flow control devices, respectively, so that the second and third flow control devices can be controlled on the basis of the data obtained from the respectively associated measuring device.

Method

An aspect of the present invention relates to a method for transporting thermal energy, comprising the following steps:

-   -   providing a hot first heat exchange medium;     -   supplying the hot first heat exchange medium into or via a first         heat exchanger, which is arranged in a sewage pipeline with a         sewage flowing direction F and thermally contacts the sewage;     -   heating the sewage by means of the first heat exchanger;     -   heating a second heat exchange medium in a second heat exchanger         by the thermal energy of the sewage, wherein the second heat         exchanger is arranged along the sewage flowing direction F in a         manner spaced from the first heat exchanger in the sewage         pipeline, and wherein the second heat exchanger thermally         contacts the sewage;     -   supplying the heated second heat exchange medium to a heat sink;     -   cooling the second heat exchange medium by means of the heat         sink.

Advantageously, thermal energy from a heat source, which is spaced from the heat sink, can be transported to the heat sink in a simple manner. Thereby, it is advantageously possible to utilize the thermal energy from heat sources and to provide it to existing heat sinks that have so far not been exploited economically. For example, thermal energy arising during cooling of industrial plants, for example stationary machines, such as printing machines, machine tools, cooling plants, chemical reactors or the like, and which so far has been released into the environment as exhaust air or sewage, can be transported to heat sinks or to heat consumers, for example to heat pumps, which provide heating energy to residential buildings. Since both industrial plants, which produce waste heat, and residential areas, which require heat for heating, are connected to the sewage system or to a sewage pipeline, it possible to transport thermal energy from the heat source to a heat sink via the sewage in a sewage pipeline with the aid of the method according to the invention in a simple and economical manner. As described above, the heat exchanger assembly necessary to perform the method according to the invention is also easy to produce. Here, already accumulated sewage is advantageously used as a thermal energy carrier medium, and particularly no further sewage heated by the heat source is introduced into the sewage pipeline, to transport the thermal energy of the heat source to the heat sink.

Providing the hot first heat exchange medium can comprise heating the first heat exchange medium by means of a heat source, wherein the heated first heat exchange medium is at least partially supplied to the first heat exchanger.

Preferably, the method further comprises the following steps:

-   -   measuring the sewage temperature T₁ by means of a first         temperature sensor arranged downstream of the first heat         exchanger in the sewage pipeline;     -   interrupting or reducing the supply of the heated first heat         exchange medium into the first heat exchanger when the measured         sewage temperature T₁ exceeds a predetermined maximum value         T_(1,max).

Advantageously, the sewage temperature T₁ does not exceed a predetermined maximum value T_(1,max) downstream of the first heat exchanger, whereby it is advantageously prevented that the evaporation rate of the sewage exceeds a predetermined value due to too high a sewage temperature T₁. The household and industrial sewages carried in a sewage pipeline usually have a sewage temperature between approximately 8° C. and approximately 20° C., wherein the sewage temperature at the inlet point into the sewage pipeline does usually not exceed 35° C. By controlling the sewage temperature T₁ downstream of the first heat exchanger, it is advantageously prevented that too strong an odor forms due to the heated sewage. Moreover, the thermal energy dissipated to the sewage from the heat source can be controlled depending on the amount of sewage. The downstream sewage temperature T₁ is preferably between approximately 8° C. and approximately 60° C. due to the thermal energy dissipation of the first heat exchanger to the sewage. The maximum sewage temperature T_(1,max) downstream of the first heat exchanger is preferably between approximately 20° C. and approximately 60° C., further preferably between approximately 25° C. and approximately 40° C. and particularly approximately 30° C.

Preferably, the method further comprises the following steps:

-   -   measuring the sewage temperature T₂ by means of a second         temperature sensor arranged downstream of the second heat         exchanger in the sewage pipeline;     -   interrupting or reducing the supply of the heated first heat         exchange medium into the first heat exchanger when the measured         sewage temperature T₂ exceeds a predetermined maximum value         T_(2,max).

It is advantageously prevented that the sewage temperature T₂ exceeds a predetermined maximum value T_(2,max) downstream of the second heat exchanger and finally reaches a sewage treatment plant or a biotope. Thereby, it is advantageously prevented that too hot a sewage acts upon a sewage treatment plant or a biotope, whereby the microfauna of the sewage treatment plant or the biotope can be affected negatively. The maximum sewage temperature T_(2,max) downstream of the second heat exchanger is preferably less than 35° C., further preferably less than 25° C. and particularly approximately 12° C.

Preferably, the method further comprises the following steps:

-   -   measuring the sewage temperature T₂ by means of a second         temperature sensor arranged downstream of the second heat         exchanger in the sewage pipeline;     -   interrupting or reducing the supply of a cold second heat         exchange medium into the second heat exchanger when the measured         sewage temperature T₂ falls below a predetermined minimum value         T_(2,min).

Advantageously, the transport of thermal energy from the sewage to the heat sink is interrupted or reduced when the sewage temperature T₂ falls below a predetermined minimum value T_(2,min), whereby it is prevented that too cold a sewage acts upon a sewage treatment plant or a biotope. Thereby, it is advantageously prevented that the biological activity of the microorganisms within the sewage treatment plant or the biotope is reduced to the low sewage temperature. Preferably, the minimum sewage temperature T_(2,min) is higher than 8° C., preferably approximately 25° C.

Preferably, the method comprises the step of throttling or damming the sewage flow through the sewage pipeline in the area of the first heat exchanger by means of the first flow control device arranged downstream of the first heat exchanger. Advantageously, by this step, a predetermined amount of cool sewage can be provided in an area of the first heat exchanger, so that the heat source can dissipate a predetermined minimum amount of thermal energy to the sewage by means of the first heat exchanger. For example, the dissipation of thermal energy produced during an industrial process can be ensured thereby, so that advantageously the uninterrupted performance of the industrial process is guaranteed. Further advantageously, the sewage can be dammed in the area of the first heat exchanger until a predetermined sewage temperature has been reached, so that advantageously the efficiency of the subsequent heat exchange at the second heat exchanger can be increased. In particular, it is not necessary to fully dam the sewage flow by means of the first flow control device, but it may be sufficient to reduce the sewage flow to a predetermined sewage flow amount per unit of time in the area of the first heat exchanger. Further preferably, throttling or damming of the sewage flow in the sewage pipeline in the area of the first heat exchanger can temporarily be suspended in full by means of the first flow control device. In particular, the sewage dammed in the area of the first heat exchanger can flow off in the form of surge flushing by abrupt opening of the flow control device along the sewage flowing direction F in the sewage pipeline, so that sedimented particles in the area of the first heat exchanger are transported further along the sewage flowing direction F in the sewage pipeline. Advantageously, cleaning of the sewage pipeline can thus be achieved at the same time.

Preferably, the method comprises the step of opening the first flow control device when the sewage has a predetermined level H₁ above the first heat exchanger and/or when the sewage has a predetermined sewage temperature T_(W1) in the area of the first heat exchanger. Since the primary purpose of a sewage pipeline is drainage, damming of the sewage in the sewage pipeline can be suspended by means of the first flow control device when a predetermined level H₁ above the first heat exchanger is reached, so that it is advantageously prevented that sewage is dammed excessively in the sewage pipeline. This can advantageously ensure a proper drainage by means of the sewage pipeline and the first flow control device. Preferably, the sewage in the area of the first heat exchanger should not exceed a predetermined sewage temperature T_(W1), since then, on the one hand, the efficiency of the thermal energy dissipation from the heat source to the sewage by means of the first heat exchanger is reduced and, on the other hand, unpleasant odors can form due to the increased sewage temperature. Therefore, the first flow control device can allow draining of the sewage along the sewage flowing direction F in the sewage pipeline when the predetermined sewage temperature T_(W1) in the area of the first heat exchanger is reached or exceeded. Here, the sewage temperature T_(W1) is selected depending on the efficiency of the heat exchange at the first heat exchanger, the efficiency of the heat exchange at the second heat exchanger arranged downstream of the first heat exchanger, the distance between the first and second heat exchangers, and the heat losses of the sewage on the way between the first heat exchanger and the second heat exchanger, as well as the local official requirements. By a suitable selection of the sewage temperature T_(W1), the first heat exchanger and the second heat exchanger can be operated in a range optimal for the given conditions, so that the amount of thermal energy transportable from the heat source to the heat sink via the first heat exchanger, the sewage, the second heat exchanger is maximal.

Advantageously, the method comprises the following steps:

-   -   detecting the thermal energy E₁ extracted by the heat sink via         the second heat exchanger;     -   detecting the thermal energy E₂ extracted by the second heat         sink via the third heat exchanger;     -   controlling the amount of sewage flowing to the second heat         exchanger and to the third heat exchanger, so that a         predetermined amount of thermal energy W₁ can be provided to the         heat sink via the second heat exchanger, and a predetermined         amount of thermal energy W₂ can be provided to the second heat         sink via the third heat exchanger.

Advantageously, the amount of sewage provided to the second heat exchanger and to the third heat exchanger can be controlled depending on the thermal energy required at the associated heat sink. Therefore, an increased amount of sewage can be provided to the second heat exchanger when the associated heat sink extracts an increased amount of thermal energy E₁.

Particularly preferably, the method comprises the step of detecting the thermal energy E_(A1) dissipated by the heat source via the first heat exchanger. Advantageously, the thermal energy E_(A1) than can be provided can be put in relation to the required energy E₁+E₂. In case that the thermal energy E_(A1) that can be provided is smaller than the required thermal energy E₁+E₂, the thermal energy E_(A1) can be distributed to the second heat exchanger and the third heat exchanger according to a predetermined ratio, so that a fraction of the required thermal energy can be provided to the heat sink and the second heat exchanger respectively. Preferably, the fraction of the thermal energy provided is the same for both heat sinks. The thermal energy still needed has to be produced by other measures at the location of the respective heat sinks and be provided there. Alternatively, the control of the amount of sewage flowing to the second heat exchanger and to the third heat exchanger can be such that the extracted thermal energy E₁ is provided substantially fully to the heat sink via the second heat exchanger or that the extracted thermal energy E₂ is provided substantially fully to the second heat sink via the third heat exchanger. A consequence would be that a small fraction of or no thermal energy can be provided to the remaining heat sink.

Since preferably a specific amount of hot sewage can be dammed in the area of the second heat exchanger or in the area of the third heat exchanger by means of an associated flow control device, wherein the thermal energy contained in the dammed sewage may be sufficient to provide the associated heat sink with thermal energy, the method preferably comprises the step of determining the thermal energy E_(A2) present in the sewage located above the second heat exchanger and/or determining the thermal energy E_(A3) present in the sewage located above the third heat exchanger. Thus, advantageously, the thermal energy that can be provided to the heat sink and the second heat can be estimated in an improved way.

The preceding description of the aspects of the invention is not limited to the respective aspects. In particular, the explanations concerning the heat exchanger assembly also apply to the method for transporting thermal energy and vice versa.

DESCRIPTION OF FIGURES

Preferred embodiments of the present invention will be described by way of example in the following on the basis of accompanying drawings. The figures show:

FIG. 1: a perspective view of an embodiment of a heat exchanger assembly;

FIG. 2: a perspective view of a further embodiment of a heat exchanger assembly.

FIG. 1 shows a perspective view of a preferred embodiment of a heat exchanger assembly 1. The heat exchanger assembly 1 comprises three first heat exchangers 11, which each have a hot water forward-run line, or hot water advance piping, 15 and a cold water return-run line, or cold water return piping, 17. It is appreciated that the heat exchanger assembly 1 may as well have one, two, four, five, or more first heat exchangers 11 next to each other or spaced from each other. The first heat exchanger 11, the hot water forward-run line 15, and the cold water return-run line 17 are filled with a first heat exchange medium 19. The first heat exchange medium 19 is in direct or indirect thermal contact with a heat source 13. Such a heat source 13 may be a cooled, industrially used machine, such as a machine tool, a printing machine, a plant for power generation, or the like. Moreover, for example, the heat source may also comprise a chemical reactor, such as devices for cooling an exothermic chemical reaction. Furthermore, the heat source may be part of a thermodynamic cycle or a heat exchanger, such as the cooling fins of a cooling unit or an air conditioning system.

Due to the thermal contact of the heat source 13 with the first heat exchange medium 19, thermal energy is transferred from the heat source 13 to the first heat exchange medium 19, i.e. the first heat exchange medium 19 is heated by the heat source 13. The first heat exchange medium 19 is supplied to the first heat exchanger 11 via the hot water forward-run line 15 e.g. by means of a circulating pump (not illustrated). The first heat exchanger 11 is introduced into a sewage pipeline 5, so that the first heat exchanger 11 thermally contacts the sewage 3 flowing in the sewage pipeline 5. For example, the first heat exchanger 11 can be introduced into an existing sewage pipeline 5 such that the first heat exchanger 11 merely rests on the bottom of the sewage pipeline 5 or alternatively is fixedly connected to the sewage pipeline 5 by being embedded in concrete. Alternatively, the sewage pipeline 5 can have a wall formed as a heat exchanger. Due to the thermal contact of the first heat exchange medium 19 with the sewage 3 via the first heat exchanger 11, the thermal energy of the first heat exchange medium 19 is partially transferred to the sewage 3, i.e. the sewage 3 is heated by the heated first heat exchange medium in the area of the first heat exchanger 11. At the same time, the first heat exchange medium 19 is cooled in the first heat exchanger 11 by the dissipation of the thermal energy to the sewage 3. The cooled heat exchange medium 19 is fed back to the heat source 13 via the cold water return-run line 17.

Depending on the slope of the sewage pipeline 5, the heated sewage 3 flows through the sewage pipeline 5 along the sewage flowing direction F. Having travelled a flow path of some hundred meters to some kilometers, the sewage 3 reaches at least one second heat exchanger 21. The second heat exchanger 21 is introduced into the sewage pipeline 5 such that the second heat exchanger 21 is in thermal contact with the sewage 3. In the second heat exchanger 21 is located a second heat exchange medium 29, which is hated by the sewage 3. The second heat exchanger 21 is hydraulically connected to a heat sink 23 by means of a hot water return-run line, or hot water return piping, 27 and a cold water forward-run line, or cold water advance piping, 25. The second heat exchange medium 29 heated by the sewage 3 is supplied to the heat sink 23 via the hot water return-run line 27 preferably by means of a circulating pump (not illustrated). The heat sink 23 is in thermal contact with the second heat exchange medium 29, so that the thermal energy stored in the second heat exchange medium 29 is partially extracted therefrom by the heat sink 23. The heat sink 23 may be part of a heat pump for heating apartments. Depending on the temperature of the second heat exchange medium 29 in the hot water return-run line 27, the heat sink 23 can also be formed as a radiator for fresh air or as a floor heating system.

The second heat exchange medium 29 is cooled due to the extraction of thermal energy from the second heat exchange medium 29 in the heat sink 23. The cooled second heat exchange medium 29 is fed back to the second heat exchanger 21 via the cold water forward-run line 25 in order to be heated there again by the sewage 3.

Preferably, the heat exchanger assembly 1 comprises a first temperature sensor 33 arranged downstream of the first heat exchanger 11. The first temperature sensor 33 detects the temperature T₁ of the sewage 3, which has been heated by the first heat exchanger 11. In order to limit the evaporation rate of the sewage 3 or to reduce unpleasant odors, the sewage temperature T₁ does preferably not exceed a predetermined maximum value t_(1,max), which preferably is approximately 60° C., further preferably 50° C., and particularly preferably 40° C. In order to limit the sewage temperature T₁ to the predetermined maximum value t_(1,max), the first temperature sensor 33 is connected to a control unit 31. The control unit 31 interrupts or reduces the supply of the heated first heat exchange medium 19 to the first heat exchanger 11 in case that the measured sewage temperature T₁ exceeds the predetermined maximum value T_(1,max).

Further preferably, the heat exchanger assembly 1 comprises a second temperature sensor 35 arranged downstream of the second heat exchanger 21. The second temperature sensor 35 detects the temperature T₂ of the sewage 3 in the sewage pipeline 5 after thermal energy has been extracted from the sewage 3 by means of the second heat exchanger 21. Since the sewage 3 is usually supplied by means of the sewage pipeline 5 of a sewage treatment plant (not illustrated), the sewage temperature T₂ of the sewage 3 in the sewage pipeline 5 should preferably be in a range between approximately 8° C. and approximately 35° C., further preferably in a range between approximately 10° C. and approximately 30° C. and particularly approximately 25° C., so that biological cleaning of the sewage 3 by microorganisms in the sewage treatment plant can take place. Too low a sewage temperature T₂ would lead to a reduced activity of the microorganisms, whereas as too high a sewage temperature T₂ leads to the death of the microorganisms in the sewage treatment plant.

The second temperature sensor 35 is preferably connected to the control unit 31, which interrupts or reduces the supply of the heated first heat exchange medium 19 to the first heat exchanger 11 when the measured sewage temperature T₂ exceeds a predetermined maximum value t_(2,max). Thus, it is advantageously prevented that too hot a sewage 3 is supplied to the downstream sewage treatment plant. Further preferably, the heat extraction from the sewage 3 is interrupted or reduced by the second heat exchanger 21, for example by interrupting or reducing the supply of the cold second heat exchange medium 29 to the second heat exchanger 21, when the measured sewage temperature T₂ falls below a predetermined minimum value T_(2,min). Interrupting or reducing the heat extraction from the sewage 3 by means of the second heat exchanger 21 can also be performed by the control unit 31, for example by means of a control valve. Alternatively, there may be provided a further control unit (not illustrated), which is connected to the second temperature sensor 35 and which controls the interruption or reduction of the heat extraction. Thus, it is advantageously prevented that too cold a sewage 3 acts on the sewage treatment plant.

It is appreciated that one or more first heat exchangers 11 can be arranged in the sewage pipeline 5 in a manner spaced from each other, or that one or more first heat exchangers 11 can be arranged in the sewage pipeline 5 in a manner connected to each other, wherein the connection of several first heat exchangers 11 can preferably be established by tension-proof and pressure-tight connection configurations at the end regions of the individual heat exchangers. Analogously, one or more second heat exchangers 21 can be arranged in the sewage pipeline 5 in a manner spaced from each other or connected to each other.

FIG. 2 shows a perspective view of a preferred embodiment of a heat exchanger assembly 1. The heat exchanger assembly 1 comprises two first heat exchangers 11, which each have a hot water forward-run line, or hot water advance piping, 15 and a cold water return-run line, or cold water return piping, 17. It is appreciated that the heat exchanger assembly 1 may as well have one, 3, 4, 5, or more first heat exchangers next to each other or spaced from each other. In correspondence to the embodiment shown in FIG. 1, a hot heat exchange medium 19 is provided to the first heat exchanger 11 via the hot water forward-run line 15, wherein the first heat exchange medium 19 is heated by means of the heat source 13. The first heat exchanger 11 is introduced into the sewage pipeline 5 such that the first heat exchanger 11 thermally contacts the sewage 3 flowing in the sewage pipeline 5. The heat exchanger 11 can be introduced into the sewage pipeline 5 as described in FIG. 1. The sewage 3 is heated by means of the heat exchanger 11, and the cooled heat exchange medium 19 is fed back to the heat source 13 via the cold water return-run line 17.

Downstream of the first heat exchanger 11 is arranged a first flow control device 37, which can control the amount of sewage flowing along the sewage flowing direction F in the sewage pipeline 5. In particular, the sewage can be dammed upstream of the flow control device 37 by means of the flow control device 37, so that an increased volume of sewage can be provided in the area of the first heat exchanger 11. Advantageously, the amount of thermal energy E_(A1) that can be dissipated to the sewage 3 can be increased thereby. The illustrated heat exchanger assembly 1 further comprises a first measuring device 37 a, which detects the level H₁ above the first heat exchanger 11 and/or the sewage temperature T_(W1) in the area of the first heat exchanger 11. The first measuring device 37 a is connected to the first flow control device 37, so that the first flow control device 37 can be opened when the sewage 3 has a predetermined level H₁ above the first heat exchanger 11 and/or when the sewage 3 has a predetermined sewage temperature T_(W1) in the area of the first heat exchanger 11.

Depending on the slope of the sewage pipeline 5, the heated sewage 3 flows through the sewage pipeline 5 along the sewage flowing direction F. Downstream of the first heat exchanger 11 is arranged at least one second heat exchanger 21. The second heat exchanger 21 is introduced into the sewage pipeline 5 such that the second heat exchanger 21 is in thermal contact with the sewage 3. A cold heat exchang medium 29 is supplied to the second heat exchanger 21 via a cold water forward-run line, or cold water advance piping, 25. The heat exchange medium 29 is heated by the sewage 3 and is supplied to a heat sink 23 via the hot water return-run line 27, the heat sink at least partially extracting the stored thermal energy from the second heat exchange medium 29. The cooled heat exchange medium 29 is then supplied to the second heat exchanger 21 via the cold water forward-run line 25.

The heat exchanger assembly 1 shown in FIG. 2 further comprises a second sewage pipeline 39, which is hydraulically connected to the sewage pipeline 5. The hydraulic connection of the sewage pipeline 5 and the second sewage pipeline 39 is established by means of a connecting shaft 53, which is arranged between the first heat exchanger 11 and the second heat exchanger 21 in the sewage pipeline 5. In the second sewage pipeline 39 is arranged a third heat exchanger 41, which is adapted to thermally contact the sewage 3 flowing in the second sewage pipeline 39. In correspondence to the second heat exchanger 21, a cold heat exchange medium 49, in particular cold wager 49, is provided to the third heat exchanger 41 via a cold water forward-run line, or cold water advance piping, 45, wherein the cool heat exchange medium 49 is heated by means of the sewage 3 via the third heat exchanger 41. The heated third heat exchange medium 49 is supplied to the second heat sink 43 via a hot water return-run line, or hot water return piping, 47 preferably by means of a circulating pump (not illustrated). The second heat sink 43 is in thermal contact with the third heat exchange medium 49, so that the thermal energy stored in the third heat exchange medium 49 is partially extracted therefrom by the second heat sink 43. The thus cooled third heat exchange medium 49 is fed back to the third heat exchanger 41 via the cold water forward-run line 45 in order to be heated there again by the sewage 3.

The second sewage pipeline 39 shown in FIG. 2 has such a slope that the sewage flowing direction in the second sewage pipeline 39 is oriented from the third heat exchanger 41 to the sewage pipeline 5. In order to supply the third heat exchanger 41 with sewage 3, which has been heated by the first heat exchanger 11, a blocking device 55 is arranged downstream of the shaft 53 in the sewage pipeline 5. By at least partially closing the blocking device 55, a predetermined fraction of the sewage 3 coming from the direction of the first heat exchanger 11 can be dammed such that the sewage rises via the shaft 53 counter to the slope of the second sewage pipeline 41 to flow to the third heat exchanger 41. Preferably, the first heat exchanger 11 is at a higher level above sea level than the third heat exchanger 41, so that the sewage 3 flows from the first heat exchanger 11 to the third heat exchanger 41 only due to gravity. Alternatively, a sewage lifting system can be connected to the sewage pipeline 5 in order to lift the sewage to a higher level, so that the sewage flows toward the third heat exchanger 41 counter to the slope of the second sewage pipeline 5.

In order to keep the sewage 3 that has flown to the third heat exchanger 41 in the area of the third heat exchanger 41, the heat exchanger assembly 1 can comprise a third flow control device 51, which throttles or dams the sewage flow through the second sewage pipeline 39 in the area of the third heat exchanger 41. in order to be heated there again by the sewage 3. Advantageously, the contact time of the sewage 3 with the third heat exchanger 41 is prolonged thereby, so that advantageously an increased amount of thermal energy can be extracted from the sewage 3. Preferably, the heat exchanger assembly 1 comprises a third measuring device 51 a, which detects the level H₃ above the third heat exchanger 41 and/or the sewage temperature T_(W3) in the area of the third heat exchanger 41. Further preferably, the third measuring device 51 a is connected to the third flow control device 51, so that the third flow control device 51 opens at least partially when the sewage 3 has a predetermined level H₃ above the third heat exchanger 41 and/or when the sewage 3 reaches a predetermined sewage temperature T_(W3) in the area of the third heat exchanger 41.

List of Reference Numerals

1 heat exchanger assembly

3 sewage

5 sewage pipeline

11 first heat exchanger

13 heat source

15 hot water forward-run line, or hot water advance piping

17 cold water return-run line, or cold water return piping

19 first heat exchange medium

21 second heat exchanger

23 heat sink

25 cold water forward-run line, or cold water advance piping

27 hot water return-run line, or hot water return piping

29 second heat exchange medium

31 control unit

33 first temperature sensor

35 second temperature sensor

37 first flow control device

39 second sewage pipeline

41 third heat exchanger

43 second heat sink

45 cold water forward-run line, or cold water advance piping

47 hot water return-run line, or hot water return piping

49 third heat exchange medium

51 third flow control device

37 a first level measuring device

51 a third level measuring device

53 connecting shaft

55 blocking device

F sewage flowing direction 

1. A heat exchanger assembly to be introduced into a sewage pipeline, the heat exchanger assembly comprising: a first heat exchanger configured to thermally conduct a heat source with sewage; a second heat exchanger configured to thermally contact the sewage with a heat sink; wherein the one second heat exchanger is arranged downstream along a sewage flowing direction in the sewage pipeline and spaced from the first heat exchanger.
 2. The heat exchanger assembly according to claim 1, further comprising a hot water forward-run line and a cold water return-run line, wherein a first heat exchange medium is heated by the heat source and supplied to the first heat exchanger by of the hot water forward-run line, and wherein the first heat exchange medium is cooled by the first heat exchanger and supplied to the heat source by the cold water return-run line.
 3. The heat exchanger assembly according to claim 1, further comprising a cold water forward-run line and a hot water return-run line, wherein a second heat exchange medium cooled by the heat sink and supplied to the second heat exchanger by the cold water forward-run line, and wherein the second heat exchange medium is heated by the second heat exchanger and supplied to the heat sink by the hot water return-run line.
 4. The heat exchanger assembly according to claim 1, further comprising a control unit, wherein the control unit is connected to a first temperature sensor and a second temperature sensor, wherein the first temperature sensor is arranged downstream of the first heat exchanger and upstream of the second heat exchanger, wherein the second temperature sensor is arranged downstream of the second heat exchanger.
 5. The heat exchanger assembly according to claim 1, further comprising: a second sewage pipeline hydraulically connectable to the sewage pipeline; a third heat exchanger configured to thermally contact the sewage with a second heat sink; wherein an amount of sewage flowing through the sewage pipeline and the second sewage pipeline is controllable.
 6. The heat exchanger assembly according to claim 5, further comprising: at least one blocking device configured to make sewage coming from the direction of the first heat exchanger flow to the second heat exchanger and to the third heat exchanger in predetermined proportions.
 7. The heat exchanger assembly according to claim 1, further comprising: a first flow control device, wherein the first flow control device is arranged downstream of the first heat exchanger; a second flow control device, wherein the second flow control device is arranged downstream of the second heat exchanger; and a third flow control device, wherein the third flow control device is arranged downstream of the third heat exchanger.
 8. The heat exchanger assembly according to claim 1, further comprising: a first measuring device configured to detect a level of the sewage in the sewage pipeline above the first heat exchanger and a temperature of the sewage proximal of the first heat exchanger; a second measuring device configured to detect a level of sewage in the sewage pipeline above the second heat exchanger and a temperature of the sewage proximal of the second heat exchanger; and a third measuring device configured to detect a level of sewage in the sewage pipeline above the third heat exchanger and a temperature of the sewage proximal of the third heat exchanger.
 9. A method for transporting thermal energy, the method comprising the steps of: providing a hot first heat exchange medium; supplying the hot first heat exchange medium into a first heat exchanger, wherein the first heat exchanger is arranged in a sewage pipeline along a sewage flowing direction and thermally contacts the sewage; heating the sewage with the first heat exchanger; heating a second heat exchange medium in a second heat exchanger with a thermal energy of the sewage, wherein the second heat exchanger is arranged along the sewage flowing direction and is spaced from the first heat exchanger in the sewage pipeline, and wherein the second heat exchanger thermally contacts the sewage; supplying the heated second heat exchange medium to a heat sink; and cooling the second heat exchange medium with the heat sink.
 10. The method according to claim 9, further comprising the steps of: measuring a sewage temperature with a first temperature sensor arranged downstream of the first heat exchanger in the sewage pipeline; and interrupting or reducing the supply of the heated first heat exchange medium into the first heat exchanger when the measured sewage temperature exceeds a predetermined maximum value.
 11. The method according to claim 9, further comprising the steps of: measuring a second sewage temperature with a second temperature sensor arranged downstream of the second heat exchanger in the sewage pipeline; interrupting or reducing the supply of the heated first heat exchange medium into the first heat exchanger when the measured second sewage temperature exceeds a predetermined maximum value.
 12. The method according to claim 9, further comprising the steps of: measuring a second sewage temperature with a second temperature sensor arranged downstream of the second heat exchanger in the sewage pipeline; interrupting or reducing a supply of a cold second heat exchange medium into the second heat exchanger when the measured sewage temperature falls below a predetermined minimum value.
 13. The method according to claim 9, further comprising the steps of: throttling or damming the sewage flowing through the sewage pipeline proximal of the first heat exchanger with a first flow control device; throttling or damming the sewage flowing through the sewage pipeline proximal of the second heat exchanger with a second flow control device; and throttling or damming the sewage flowing through a second sewage pipeline proximal of a third heat exchanger with a third flow control device.
 14. The method according to claim 13, further comprising the steps of: opening the first flow control device when a level of the sewage above the first heat exchanger is at a predetermined level or when a temperature of the sewage proximal of the first heat exchanger is at a predetermined sewage temperature; opening the second flow control device when a level of the sewage above the second heat exchanger is at a predetermined level or when a temperature of the sewage proximal of the second heat exchanger is at a predetermined sewage temperature; and opening the third flow control device when a level of the sewage above the third heat exchanger is at a predetermined level or when a temperature of the sewage proximal of the third heat exchanger is at a predetermined sewage temperature.
 15. The method according to claim 9, further comprising the following steps: detecting a first thermal energy extracted by the heat sink via the second heat exchanger; detecting a second thermal energy extracted by a second heat sink via a third heat exchanger; controlling an amount of sewage flowing to the second heat exchanger and to the third heat exchanger, so that a first predetermined amount of thermal energy can be provided to the heat sink via the second heat exchanger, and a second predetermined amount of thermal energy can be provided to the second heat sink via the third heat exchanger. 